1. Field of the Invention
The present invention relates to technology relating to matrix type plasma display panel (PDP) and more particularly to technology relating to plasma display panel whose drive power supply is automatically adjusted.
2. Description of the Related Art
Since before, it has been well known that reactive power can be decreased in sustain period because if the resonance frequency of the sustain circuit is reduced in a drive circuit of the PDP unit, a current peak value at the time of resonance is decreased, so that effective current is also decreased.
The sustain circuit mentioned here refers to a circuit for supplying electric power to a discharge cell in order to sustain discharge in a stable condition and the sustain period refers to a period in which light emission of the discharge cell is repeated by the sustain circuit so as to maintain the light emission condition.
Conventional technology about the driving circuit of the PDP unit has been disclosed in Japanese Patent Application Laid-Open No. 2000-293135.
However, if the resonance frequency of the sustain circuit is decreased, there is a trouble that it leads to changing discharge condition thereby affecting discharge margin and discharge intensity.
The above-mentioned Japanese Patent Application Laid-Open No. 2000-293135 does not describe any special matter about reduction of reactive power by operating the resonance frequency of the sustain circuit.
An object of the present invention is to provide a drive circuit of the PDP unit capable of operating the resonance frequency of the sustain circuit so as to reduce reactive power in a circuit in the sustain period without affecting discharge margin and discharge intensity.
A drive circuit of PDP unit including at least a pair of electrodes and discharge cells connected thereto, is further provided: a first path having a first switch and a first coil for applying voltage to the discharge cells; a second path having a second switch and a second coil for expelling the voltage applied to the discharge cells; and electric charge accumulating devices connected to the first path and the second path, wherein the inductance value of the second coil is larger than the inductance value of the first coil.
Consequently, according to the present invention, the resonance frequency at the time of fall, which does not affect discharge condition, can be reduced while maintaining a conventional resonance frequency at the time of leading, which affects the discharge condition. Thus, the peak value of current upon resonance can be reduced and effective current can be reduced, so that reactive power in a circuit in the sustain period can be reduced.